New Images of Tumbling US Satellite From Theirry Legaullt

The BBC reports that "An amateur astronomer has recorded images of the out-of-control US satellite as it tumbles back to Earth. Theirry Legault, from Paris, captured the video as the satellite passed over northern France on 15 September. The six-tonne, 20-year-old spacecraft has fallen out of orbit and is expected to crash somewhere on Earth on or around 24 September. The US space agency says the risk to life from the Upper Atmosphere Research Satellite (UARS) is 1 in 3,200. Mr Legault, an engineer, used a specially designed camera to record the tumbling satellite through his 14-inch telescope, posting the footage on his Astrophotography website." (Previous, equally impressive work from Legault include his photos of Atlantis's final re-entry and the ISS, sun and moon in one shot.)

Previously hit by space debris

[popoutman]

Thierry Legault has done some wonderful captures of satellites as they've gone overhead. It's interesting to see the slow tumble of this particular satellite, which confirms that it's pretty much out of action (even though we already know that). Apparently the satellite had a possible minor collision with debris in 2007 (see page 15 of 52 of http://www.ucsusa.org/assets/documents/nwgs/securing-the-skies-full-report-1.pdf [ucsusa.org] ) which is the likely reason that this satellite is tumbling.

Re:Anyone know why the satelite is out of control?

[popoutman]

To my knowledge, the amount of fuel remaining was used to guarantee that it would re-enter sooner rather than later (a 25kg of fuel burn was executed at the end of 2005). There were plans mooted to recover the UARS using the Shuttle, but this fell by the wayside with various budget cuts and safety concerns. It appears that there was no need to have de-orbit fuel kept when the shuttle was the recovery vehicle, and when the plans fell through there wasn't enough fuel left to de-orbit in a known manner. The advantage of using the fuel in hte meantime allowed a few more years of data gathering. The working altitude for UARS was never going to have a safe parking orbit, and the orbit of the ISS was close enough in 2010 that an avoidance manouevre was needed to reduce the possibility of an impact. The spacecraft was left in a known stable attitude, but as the tumbling has shown, there has been an outside influence to cause this level of rotation. Maybe a pebble-sized item collided, and this is what's causing the tens-of-seconds wobble.